Mitogen activated protein kinases (MAPKs) comprise an evolutionarily conserved family of signal transducing enzymes that phosphorylate regulatory molecules in response to a broad variety of upstream signals. MAPKs are required for adaptive responses to changes in the environment, proliferative responses to mitogens, and differentiative responses to signals that occur during development. An important issue that is relevant to embryological development and the control of cell proliferation concerns how MAPK pathways regulate developmental processes. SMK1, encodes a MAPK that is required for meiotic development an excellent model system for development. This study will use SMK1 and sporulation to elucidate molecular mechanisms in MAPK signaling pathways that regulate cellular differentiation programs. A collection of conditional smk1 mutants has already been generated and characterized at the genetic, biochemical and ultrastructural levels (Wagner et al. 1999, Genetics 151:1327). In aim 1 of this proposal these mutants will be used to: Identify new components of the SMK1 signaling pathways using sensitized genetic backgrounds. In order to ground the inferences from these genetic studies in biochemical mechanism it is necessary to develop biochemical approaches to study Smk1. In aim 2 studies we will: Elucidate the role of the spindle pole body in regulating SMK1 function. In cells (Pierce et a. 1998, Mol. Cell. Biol. 18:5970, i.e. et al. EMO J. in press). In aim 4 experiments are described that will: Elucidate the role of the SMK1 transcriptional regulatory pathway in controlling progression of meiotic development.